28 



Gr. 0. SARS. 



[No. 1. 



the antennulæ and dividing at their extremity into a number of 

 nerve-fibres, which end with numerous ganglionic cells, filling up 

 the dilated terminal part of these organs at the base of the 

 sensory filaments (see fig. 6). The antennal nerves do not seem 

 to arise from the cerebral ganglion itself, but from the strong 

 commissures encompassing the æsophagus. The closer structure 

 of these nerves and the mode by which they innervate the several 

 parts of the antennæ, I have not succeeded in tracing out. 



As to the ventral chain of ganglia, this part of the nervous 

 system is very difficult to examine, and especially the anterior 

 part of this chain is so completely hidden by the oral parts as 

 to quite escape observation. By carefully dissecting the trunk, 

 and spreading it out in a ventral aspect after the intestine had 

 been removed, I have, however, succeeded in partly tracing out 

 the double nervous cord, which seems to agree in structure pre- 

 cisely with that in other known Phyllopoda, exhibiting the pe- 

 culiar ladder-like appearance characteristic of those animals. 



b. Tite Digestive System. 



The oral orifice, located between the masticatory parts of 

 the mandibles, is generally covered below by the labrum. It 

 leads to a short and narrow æsophagus, which ascends almost 

 perpendicularly to the intestine, in the inner cavity of which it 

 forms a distinct mammillar projection (see Pl. III, fig. 5). The 

 walls of the æsophagus are highly muscular, and its contours 

 wavy from the strong circular muscles. Besides, numerous fine 

 muscular bundles forming a continuation of the transverse 

 muscles of the labrum mentioned above, are found adjoining 

 its anterior wall. The intestine (see Pl. I, fig. 3, Pl. II, PL 

 VIII, figs. 1, 4), as in the other forms of this group of Phyllo- 

 poda, constitutes a rather wide and uniform tube, running along 

 the axis of the body and but very slightly dilated in its 

 anterior part, that curves more or less abruptly downward, 

 according to the attitude of the head. The foremost part of the 

 intestine, extended within the preoral part of the head, expands. 



